UK Clinical Pharmacy Association


Issues for surgery

Reduction in intentional weight loss (due to increased dietary fat absorption) if omitted.

Potential problems with toileting in post-operative patient if continued. 

Advice in the perioperative period

Elective and emergency surgery 

Miss dose(s) of orlistat while the patient is fasting.

Post-operative advice

If a meal is missed or contains no fat, the dose of orlistat should be omitted. 

Due to gastrointestinal side effects (including faecal urgency, liquid stools and faecal incontinence), patients may prefer to withhold orlistat as an inpatient particularly if they are less mobile post-operatively. 

Interactions with common anaesthetic agents


Interactions with other common medicines used in the perioperative period


However, orlistat might affect the absorption of concurrently administered drugs – consider separating administration, particularly with critical medications or drugs that have a narrow therapeutic index.

Further information

None relevant.


Summary of Product Characteristics – Orlistat 120mg hard capsules. Amneal Pharma Europe Limited. Accessed via 23/07/2019 [date of revision of the text June 2016]

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. [Accessed on 23rd July 2019]

Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 23rd July 2019]

Orlistat. In: Brayfield A (Ed), Martindale: The Complete Drug Reference. London: The Royal Pharmaceutical Society of Great Britain. Electronic version. Truven Health Analytics, Greenwood Village, Colorado, USA. Available at: [Accessed 23rd July 2019]